Research in Context
Tree species diversity.
Mapping of rare species in Athens
For many decades tree species diversity has been a goal for urban forest management, regardless of climate change considerations. The negative impact of relying on a handful of species has long been documented.
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The development of tree inventories has been advanced in recent years with new technologies (LIDAR). Monitoring urban tree performance in a systemic way can be a significand aid for tree management and urban planning.
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Surveying for species that are rarely used in the area's urban environment is an essential element for many research programs on trees for the future (ARDEM project, California). Exploring their potential for resilience could lead to the enrichment of the planting palette.
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I have conducted a tree survey in Athens, recording species that are not commonly used in most boroughs. Since autumn 2023, more than one hundred species have been recorded and mapped, including shrub species that can be trained as small trees. A selection of forty species is presented here. The evaluation of their performance is based on personal observations.
The tree survey is ongoing. Observations have been collected from more than twenty boroughs of the metropolitan area of Athens, at various types of public green spaces such as street rows, parks etc.
​Among the large parks that have been surveyed are:
- The National Garden of Athens which is host for many exotic species
- Ancient Agora which is host to native species, rarely found in the urban environment
- Alsos Sygrou
- Alsos Nea Smirni
- NTUA campus​​​​​​​​
Tree row with monumental palm trees Washingtonia filifera at the entrance of the National Garden. Since the mid-19th century, the historical garden has served as a point of entry and testing for many introduced species. Image credit: Aggeliki Christodoulou 2016
Some of the species in the survey list are fairly unknown to the general public. They have though an aesthetic interest (flowering, fruit, bark) or significant shade capacity and they merit to be considered for further use.
Various comprehensive databases were used for the description of each species:
- ​Data about the presence of each species in cities worldwide were derived from the Global Urban Tree Inventory (GUTI) which was created by the research team for the Australian project "Which Plant Where". ​
- The database Plants of the World Online (POWO) which is published by the Royal Botanic Gardens of Kew was the source for the area of origin, global distribution (countries or regions) and biomes​
- Supplementary data were extracted from Trees and Shrubs Online, developed by the International Dendrology Society.​
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Distribution of tree species worldwide, either as urban trees in cities or naturalized in other environments, may be useful in the quest for suitable species for the urban tree canopy of Athens. ​Therefore detailed information from the databases is reproduced for each species.
It is to be noted that listings by Kew Gardens POWO database include besides countries and some geographical entities that correspond to distinct ecosystems and environmental conditions.
Also the GUTI database does not include all urban tree inventories. Therefore for some tree species it is likely they occur in more cities, particularly the cosmopolitan ones.
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The identification of the tree species was aided by the app iNaturalist. Available from https://www.inaturalist.org.
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For the recording and mapping of the locations of the rare species the tool "Google My Maps" has been used.
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Literature references have been added for species that have attracted the interest of research for suitability for future climate conditions.​
​​​​Note: With only one exception, all photos of the tree survey are from the personal archive. They were taken over the course of two years, from autumn 2023 until autumn 2025.
Aesculus x carnea
Sapindaceae
Taxonomy
This is an artificial hybrid. The hybrid formula of this artificial cross is A. hippocastanum × A. pavia.
Distribution in Athens. Extremely rare in Athens. Only a few trees at a single site were recorded at the northern borough of Dionysos. Outside a house, on the side of a central highway.
Cities worldwide
Tree inventories in cities around the world.
The parent species Aesculus pavia is found in 22 tree inventories.
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DATABASES
The Global Urban Tree Inventory: A database of the diverse tree flora that inhabits the world’s cities. Global Ecol Biogeography 29:1907-1914. (2020).
https://doi.org/10.1111/geb.13169.
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Royal Botanic Gardens, Kew. Plants of the World Online | Kew Science. [online] Plants of the World Online. https://powo.science.kew.org/.
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Trees and Shrubs Online - A modern reference to temperate woody plants.